Isotopes solutions

Enriched cadmium isotopic standard (Spectrascan Stable Isotope Solution, Teknolab A/S, P.O. Box 131, N-1441 Drobak, Norway). 

Precipitation of Hafnium Hydroxide. In order to interpret the adsorption data it was necessary to determine the conditions which lead to the precipitation of hafnium hydroxide. It is not usually advisable to depend on the solubility product because the information on this quantity is often unreliable for hydroxides of polyvalent metal ions. In addition, "radiocolloids may apparently form much below saturation conditions in radioactive isotope solutions. In the specific case of hafnium hydroxide only two measurements of the solubility seem to have been reported. According to Larson and Gammill (16) K8 = [Hf(OH)22+] [OH ]2 — 4 X 10"26 assuming the existence of only one hydrolyzed species Hf(OH)22+. The second reported value is Kso = [Hf4+] [OH-]4 = 3.7 X 10 55 (15). If one uses the solubility data by Larson and Gammill (Ref. 16, Tables I and III) and takes into consideration all monomeric hafnium species (23) a KBO value of 4 X 10 58 is calculated. 

In the present study, bread in the form of rolls was prepared from whole grain flour (100% extraction rate) with a zinc content of 22 mg/kg and from white wheat flour of about 72% extraction rate, where the zinc content was 7 mg/kg. The water added to the dough, contained an amount of almost carrier free isotope solution, corresponding to 0.25y/ Ci of Zn for each roll. The isotope solution was made by diluting a stock solution of 65 Zn CI2 in 0.1 M HCl (0.1 to 0.5 Ci/g Zn, Radiochemical centre, Amersham, England) with physiological saline to a final radioactivity of Ci/ml. 

This pilot study with a small number of infants does not permit firm conclusions about metal absorption in infants However we have learned that bottle-fed infants tolerate the metal isotope solutions better than breast-fed infants In a subsequent study many (6/20) breast-fed babies spit up the milk-isotope mixture within 30 minutes of feeding Two others refused it entirely In contrasty all bottle-fed babies (12/12) drank the isotope-formula mixture and none had emesis The doses of isotopes could probably be reduced by at least half without sacrificing analytical sensitivity and this would probably reduce gastrointestinal intolerance ... 

The solutions of eqns (5.62)-(5.64) in this approximation fully determine the dependences on c of not only the intensities and positions of the light absorption bands for a crystal but also the dispersion of the refractive indexes. The above equations can be readily extended to the case of multicomponent isotopic solutions. Then eqns (5.36) and (5.63) retain their form but eqns (5.37), (5.62), and (5.64), respectively, are replaced by the more general equations ... 

Some medically useful isotopes, with short half-lives, must be prepared near the site of the clinical test. Preparation and shipment from a reactor site would waste time and result in an isotopic solution that had already undergone significant decay, resulting in diminished activity. 

Isotopes Solute in water Electrode Separation factor Reference... 

Quantity Unit Enriched isotope solution Natural isotope solution... 

In an experiment two of the sample vessels contain the two different Isotopic solutions. The pressure difference between them is monitored to approximately. 03% or 11).001 mm, whichever Is larger. The other two vessels contain a solution of the normal Isomer being compared against a standard solution, pure solvent, or vacuum. One run over the temperature range therefore furnishes us with a set of data on the total pressure and the Isotopic pressure ratio as a function of temperature. 

The determination of equilibrium constants for heterogeneous isotope-exchange reactions involving isotope-exchange between pure phases and solution phases yields partition-function ratios for the isotopic, solution-phase species. In favorable cases a comparison of calculated values for the solute partition-function ratio with the experimental value allows one to distinguish between possible solute models. 

In other words the treatment of solution-phase species (i.e. talcing = K52) s>s gas-phase species is equivalent to the assumption that there is no isotope effect on the Henry s law constant for the isotopic solutes. 

III.c. Evaluation of Partition-Function Ratios for Isotopic Solute Species. The Symmetric Solvent Case. 

The extraction process for radioisotopes is a combined chemical/distillation process in which the noble gases and iodine are first condensed from the target fill gas. Next, the UO2 fuel and fission products are dissolved from the inside of the target in an acidic solution and a wet chemistry process is used to selectively precipitate isotopes of interest. The precipitates are further washed, filtered, redissolved and purified. Finally, the isotope solution is prepared for shipment. 

Figure 2 Elution curve for self-sharpening band displacement of a di-isotopic solute ion on an ion exchange column. (A) The isotopic ratio Rasa function of the distance x that the band was displaced. (B) Total concentration C of the ion as a function of x. For the other descriptors see the section on production of separated isotopes.

A stock solution was prepared by dissolving the enriched isotope. Diluted solutions were prepared from this stock solution on a weight basis. The isotopic composition of this solution was determined experimentally by GC-MS analysis of the chelate. The internal standard solution was calibrated by reverse isotope dilution GC-MS using the atomic absorption primary standard. Weighed amounts of the primary standard solution were mixed with weighed amounts of the enriched isotope solution. Chelates were prepared from the spiked samples (as described below) and were used for mass spectrometric determination of isotope ratios. Concentration of the trace metal in the spike solution was calculated using the experimentally determined isotope ratios, the weights of the standard and... 

Organisms given food-plant grown in, dipped in, or otherwise treated with isotope solution. (8, 25, 29, 33, 40, 41, 53, 64, 65)... 

Isotope solution placed between mouthparts with pipette. (49 )... 

Deposits of Metamorphic Origin in Much Older Rocks. Lead isotope data clearly support a metamorphic origin for some deposits of this kind although well-documented studies are few for this little-emphasized category. In order to have a good isotopic solution, the metamorphism... 

There are two common stable isotopes of helium, He and He, with relative abundancies of lO" and 100%, respectively. Neither isotope has a triple point in the phase diagram, and when mixed, they provide the only case in which isotopic mixtures form two liquid phases in equilibrium, the isotopic solutions separating below 0.87 K. 

In polar systems like methanol-carbon tetrachloride (cf. Ch. XV) the excess functions are greater by a factor of about 10. On tlie contrary for isotopic solutions (He -He, D2-H2, cf. Ch. XIX) the excess free energy is of the order of 1 calorie or even less. As showm on Fig, 1.7.1, g is negative (activity coefficients smaller than I) for the system -heptane -j- -hexadecane, while it is positive in the other three systems. We say that in the case 1.7.1, we have negative deviations... 

It may be interesting to observe that it is possible to express the excess functions of the isotopic solutions in terms of the properties of prue isotopes without the introduction of any new parameter. This is quite different from the case of ordinary solutions where the thermodynamic properties depend not only on the properties of the pure compounds but also on new interaction parameters like sab, which clearly cannot be obtained from the study of the pure compounds. From this point of view, the problem of isotopic mixtures is much simpler because here no new parameters appear in the hamiltonian of the mixture. 

Coulometry can be classified as a macro method, involving grams of sample. The use of submilligram samples in coulometry, on the other hand, classifies it equally well as a micro method. High-precision coulometry has been widely used for the determination of major constituents of various materials. Determination of trace impurities, e.g., dopants such as chromium in ruby lasers, has been performed at the nanogram level. It has been used successfully for the determination of stoichiometry of materials such as GaAs, for measurement of physical constants such as the faraday and atomic weights, for determination of major constituents of Standard Reference Materials, and for the analysis of important research materials such as separated isotope solutions. 

Measured on isotopic solute containing 2.43 atoms deuterium per molecule tabulated value is not corrected for isotopic deficiency. 

Measured on isotopic solute containing 100% of theoretical deuterium content. 

The reported (89) deficiency of deuterium (78% of theoretical) was found to be erroneous. Proton magnetic resonanfte detected no H in the isotopic solute. 

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